Printing device with moveable characters

ABSTRACT

A printing device including a type carrier and a writing medium, the type carrier being actuated so as to advance with respect to the writing medium, and a striking arrangement for applying mechanical strike pulses by means of hammers to the print medium. According to the invention, the device is characterized in that the type carrier is made of an element, at least partially coated with a material with great damping ability which supports an assembly of shoes, each of said shoes carries at least one type character and is introduced into said material so as to be able to move in its housing when a mechanical strike pulse is applied to the type supported in the shoes. The invention is applicable to linear type carrier printers or to drum, wheel or disc printers.

United States Patent [191 Deproux I PRINTING DEVICE WITH MOVEABLE CHARACTERS [75] Inventor: Jacques Roland Deproux, Sevres,

France [73] Assignee: Societe Industrielle Honeywell Bull (Societe Anonyme), Paris, France 22 Filed: Dec. 18, 1972 21 Appl. No: 316,171

[30] Foreign Application Priority Data Dec. 28, 1971 France 71.47026 [52] US. Cl 197/53, 101/377, 197/18, 101/111 [51] Int. Cl B41j 1/32 [58] Field of Search 197/18, 53, 57, 36; 101/370, 376, 377, 380, 109-111, 98, 368, 103, 93; 40/140 [56] References Cited UNITED STATES PATENTS 453,699 6/1891 Hoggson 101/111 2,762,297 9/1956 Baer l0l/lll X 2,987,991 6/1961 Johnson, Jr. ct al.... 101/376 X 3,186,337 6/1965 Hill 101/377 X 3,209,682 10/1965 Cooper, Jr. et a1... 101/111 X 3,230,880 1/1966 Beaver 101/376 X 3,465,673 9/1969 Oppenheim 101/377 x 1 Oct. 1,1974

3,640,369 2/1972 Rolph 197/53 3,667,384 6/1972 Sniderman lOl/lll 3,683,802 8/1972 Hepner et al. 101/1 11 3,717,234 2/1973 Kollerml 197/18 FOREIGN PATENTS OR APPLICATIONS Primary Examiner-Robert E. Pulfrey Assistant Examiner-E. H. Eickholt Attorney, Agent, or Firm-Fred Iacob [5 7 ABSTRACT A printing device including a type carrier and a writing medium, the type carrier being actuated so as to advance with respect to the writing medium, and a striking arrangement for applying mechanical strike pulses by means of hammers to the print medium. According to the invention, the device is characterized in that the type carrier is made of an element, at least partially coated with a material with great damping ability which supports an assembly of shoes, each of said shoes carries at least one type character and is introduced into said material so as to be able to move in its housing when a mechanical strike pulse is applied to the type supported in the shoes. The invention is applicable to linear type carrier printers or to drum, wheel or disc printers.

15 Claims, 12 Drawing Figures 2/1954 Germany 101/379 PRINTING DEVICE WITH MOVEABLE CHARACTERS FIELD OF THE INVENTION The presentinvention deals with a printing device with movable characters, designed particularly for linear-type carrier printers or drum printers.

BACKGROUND OF THE INVENTION Printers with a linear-type carrier or with a drum comprise a writing medium in front of a moving type carrier and a printing set including printing motors. Everyone of these motors is capable of sequentially applying strike pulses to the characters by means of a striking hammer.

The output demanded of these printers is constantly on the increase. The attainment of printing speeds of 1,000 to 2,000 lines per minutes is quite frequent. To achieve such performances, the speed'at which the type carrier passes the print medium has to be quite high. Machines presently exist which are capable of attaining passing speeds on the order of to 6 meters/second. This entails certain drawbacks for the type carrier does not stop during the strike of the characters but rather continues passing at high velocity. Thus when a printing motor is actuated there occurs during the impact with the chosen character, a sizeable friction force which is parallel to and in the same direction as the passing velocity. This force has the tendency to pull the writing medium along to asignificant degree in the direction of the passage of the characters which is obviously detrimental the printing quality. The linear-type carrier printers in which the carrier is an endless belt pose'still other problems because of their special structure. The endless belt is usually equipped with elastic type-carrying tongues on one rim so that the characters are positioned at the very ends of these tongues. When, therefore, the character receives the impact of a printing hammer the type-carrying tongue is deformed so as to permit a struck character to remain in front of the corresponding printing position as long as the impact of the hammer lasts. Apparently, if one wishes to raise substantially the performance of these machines by increasing the passing speed 5 or 6 m/s) the tongues become subjected to marked stresses and the frequent repetition of these stresses entails the risk of a reduction of the working life of the tongues. The furthermore fact that the type-carrying tongues are placed on the rim of a belt, causes the belt to tend to an S shape when several characters are struck simultaneously. The result is a reduced working life duration for the belt as well as a disalignment of the printed characters.

SUMMARY OF THE INVENTION The present invention eliminates the aforementioned drawbacks by making use of the principle of the movable strike by oscillating characters. According to the invention the printing device includes a type carrier and a writing medium, wherein the type carrier moves past the writing medium. Furthermore, a printing set applys strike pulses to the print medium by means of hammers, so that the writing medium is thereby placed in contact with the type carrier when the pulses are applied. The type carrier consists of an element which is at least partially coated with a material with great damping ability. The type carrier contains a set of shoes each of which holds at least one type character and is enclosed in said material. The type character is capable of moving in its enclosure when a strike pulse is applied to it. The material is preferably a substance such as a visco-elastic elastomer. In a preferred embodiment of the invention, the type carrier is an endless belt mounted on two pullies. In another embodiment of the inventioon the type carrier is a cylindrical drum. It is preferable that the shoes be individually insertable into said material which is in turn cemented onto the carrier element.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood by the following description presented with reference to the attached drawings wherein:

FIG. 1 is a perspective view of the type carrier according to the invention.

FIG. 2a is an enlarged vertical sectional view through a portion of the type carrier of FIG. 1 along the line A,A' of FIG. 2b and shows the type carrier in more detail.

FIG. 2b is an enlarged elevational view of a portion of the type carrier.

FIG. 2c is an enlarged plan view of a portion of the type carrier in position relative to a writing medium and impacting means.

FIGS. 3 and 4 are perspective views of a typecarrying shoe and the shock-absorbers between which it is positioned.

FIG. 5 illustrates the ease with which characters may be interchanged.

FIGS. 6a, 6b, 6c and 6d are schematic plan views showing the different phases of operation of a printing device with a type carrier such as shown in FIG. 1. FIG. 7 demonstrates an alternative embodiment of the type carrier device according to the invention.

DETAILED DESCRIPTION OF THE INVENTION FIG. 1 is a perspective view exemplifying a type carrier which may be used with the invention. The carrier is an endless belt (1) on two pullies (not shown) within the printer. The pullies are symbolized by their vertical rotational axes Y,, Y and Y Y To facilitate an understanding of this illustration, only one part (2) of the belt is shown with its characters intentionally oversized in relation to it so as to make them more distinct. This part (2) is illustrated on an even higher scale in FIGS. 2a and 2b.

The part (2) includes as illustrated in FIGS. 1, 2a and 2b, type-holding shoes (4) to (7) and corresponding characters (8) to (11), visco-elastic shock-absorbers (12) to (17) and synchronization apertures (18) to (22) as well as a metallic core (23) of the type-carrier (1). For a better understanding of the invention, the type-carrying shoe 5 and its character (9) are shown in perspective in FIG. 3. It is to be appreciated that all other character-holding shoes are identical. For reasons of convenience, only a single character is shown in the shoes of FIGS. 2b and 3. It is obvious, though, that the invention is by no means limited to shoes carrying a single character, and that it: is equally applicable to shoes holding several types, positioned, i.e., one above the other.

The shoe (3) is placed between the shock-absorbers 12) and (13) and within the location (30) (which is shown in FIG. 2b). Each shoe (3) to (7) is positioned between two visco-elastic dampers. Thus, for example, the shoe (4) is enclosed between the shock-absorbers (l3) and (14). When the type-carrying belt (1) moves with the velocity V in the direction indicated by the arrow (FIG. 2c) then the shock-absorber (14) is termed the downstream damper for shoe (4) and the shock-absorber (13) is called the upstream damper. With respect to shoe the shock-absorber (14) is the upstream damper and the shock-absorber (15) is the downstream damper. These visco-elastic shockabsorbers may for example be made of an elastomer material which is cemented to the metallic core (23). Then the flutings (3A), (4A), (5A) are cut into the body of the material. It goes without saying that the invention is not restricted to shock-absorbers built into an elastomer material. The invention is directed to any damper constructed of any material of a low energyrestoring power. The shock-absorbers (12) to (17) are deemed independent units from a functional point of view. This is justified by their behavior in practice.

In FIGS. 20 the shoes (5), (6), (7), and the corresponding characters (9), (10), (11), as well as three striking hammers (24), (25 (26), the writing medium (27) and the ink ribbon (28) are shown. The three striking hammers can be inclined in relation to the writing medium (27), as described in the French Pat. application No. 7 l/42,937 filed on Nov. 30, 1971 for a Printer with an Inclined Printing Module. The invention is obviously not limited to such an arrangement of hammers and is equally useful for hammers positioned perpendicularly to the direction of the passing characters. In rest position, when the characters are not struck by the hammers the sides (41), (51), (61), (71) of the shoes (4) to (7) are pressed against their respective downstream shock-absorbers while the sides (42) to (72) have no contact with their respective upstream shock-absorber. For this reason, if the shoes (5) to (7) are considered from above as illustrated in FIG. 20 they are inclined by an anglea relative to the perpendiculars B 8 C C D D to the core (23) of the carrier (1), passing through points 0 0 0 A preferably solid lubricant is inserted and pressed into each space left open between each socket (5), (6), (7) and the upstream and downstream dampers, namely (14) and (15) and (l6), (l6) and (17). The lubricant enables each shoe to oscillate with greater ease between the downstream and the upstream shock-absorber when the character corresponding with this shoe is struck by one of the hammers. The lubricant, furthermore, facilitates the entering of the typecarrying shoes between the shock-absorbers. The various phases of this insertion are illustrated in FIG. 5. The shoe (5) is not inserted, the shoe (7) has fully entered, the shoe (6) takes on an intermediate position. As may be seen in this illustration, a pair of pincers (29) are shown partly in dashed lines which is all that is necessary to insert the socket (6) between the shockabsorber (15) and (16) by exertion of a simple pressure so that the expansion of the shoe in its end part (top of the illustration) accomplishes a sufficient locking. It goes withiout saying that the same holds for each typecarrying shoe. It may be seen then that exchanging one type-holding shoe with another is easy. It is feasible to insert shoes from the top also, provided that shoes and shock-absorbers are given a different shape.

The operation of the printing device according to the invention is illustrated in FIG. 6. Shoe (6) and its downstream shockabsorber (l6) and its upstream shockabsorber 15) is taken as an example. It is assumed that the hammer (25), for instance, is set in motion by its printing motor and that it supplies a striking pulse Jo. The print of the character (11) may be divided into four phases which are: begin middle end of print and finally return of the shoe (6) and its character (10) to their initial position. These four phases are illustrated respectively in the FIG. 6a, 6b, 6c, 6d and are described hereinafter.

FIRST PHASE: START OF PRINT (FIG. 6a)

This phase corresponds with the initial contact of the character 10 with the ribbon. It is assumed that this is the instant in which contact begins. A reference mark A is to be assumed attached to the metallic core (23) of the type carrier (1) and it is also assumed that this reference mark faces a fixed reference mark 0. Assuming again that the velocity of the carrier movement is V,,. The velocity, V of the carrier movement, the shoe (6) is in complete contact with its downstream shockabsorber (16) and touches tangentially the metallic core (23) of the belt (1) at the point 8,. Because of the effect of the striking pulse .1 from the hammer, a force F is experienced at point D the contact point of the character l0) and the ribbon (28). This force is relatively weak. Yet since the distance L between the point S, and the carrier of that force F,, is large the torque exerted on the shoe (6) and the character (10) in the direction of the arrow F, is strong and makes it possible to markedly reduce the initial drag which acts against the setting in motion of the type-carrying shoe (6). The latter begins to move in the direction of the arrow F, and detaches itself from its downstream damper (16) to move towards the upstream shockabsorber (15) which brakes its speed only slightly since it is only partially in contact with the shoe (6). The point D leaves a trace D on the ribbon.

SECOND PHASE: MIDDLE OF THE PRINT (FIG. 6b)

The type-carrier has advanced a distance equal to e/2 in relation to the reference mark 0 wherein e V xt in which r is the total contact time of the character with the ribbon during the impression. It is assumed that S is the tangent point of the shoe with the core (23) coinciding with A during this phase. M is the contact point of the ribbon (28) with the character (11). The impact force F is applied at this point and is at a maximum. It is to be noted however, that the lever arm is reduced which tends to limit the increase of the torque. This torque always has the tendency of pulling the shoe (6) toward the upstream shockabsorber (15) in the direction of the arrow Fl. Since the contact surface between the shoe (6) and this damper (the upstream shock-absorber) is larger than in the preceding phase the braking of the type-carrying shoe is stronger. The initial position of the upstream shockabsorber (15) in FIG. 6b is illustrated by a dotted line (corresponding with phase 1). Point M leaves a trace M' on the ribbon.

THIRD PHASE: END OF IMPRESSION (FIG.

This phase corresponds with the contact end between character (10) and ribbon (28). The reference mark A of the carrier (1) has advanced by a quantity 5 corresponding with the total contact time to. It is assumed that S is the tangent point between the shoe (6) and the core (23) and F the contact point between the character (I) and the ribbon (28). The impact force F is then weak. However, the upstream shockabsorber has been sharply squeezed and the braking is extremely forceful. These two conditions, carried out simultaneously, bring about the return of the shoe (6) to its downstream shock absorber and facilitates its rapid return to its initial position. Point F leaves a trace F on the ribbon. The shape of the upstream shockabsorber is so calculated that the braking of the shoe is as efficient as possible.

FOURTH PHASE: RETURN OF CHARACTER TO ITS INITIAL POSITION (FIG. 6d).

The reference mark A of the carrier (I) has advanced by a quality E Voxt in which t,. is called restoration time of the type-carrying shoe. During this phase, the shoe is only subjected to the stresses of the shockabsorbers. Launched and accelerated by the upstream damper (I5) it reaches the downstream shockabsorber (I6) with a highly reduced energy, yet sufficient to compress the latter. After some very short oscillations of weak amplitude the shoe becomes stabilized in its initial position (the one of phase I). In FIG. 6d the position of the shoe (6) is denoted in dashed lines when it compresses the downstream shockabsorber (I6). The shape of the downstream damper is so calculated that the shock-absorption of the shoe (6) occurs in the shortest time. In the first and second phases as well as in the fourth phase, the shock-absorbers (I5) and (I6) are relatively little affected and compressed by the shoe (6). Risks of a disturbance of neighboring type-carrying shoes, and hence flutter, is practically non existant. In the third phase (end of impression), on the other hand, the shock-absorber is strongly compressed and there is a risk of disturbing the adjoining type-carrying shoe. It is for this reason that the form and the nature of the shock-absorbers are subjected to a special examination so that the risks of flutter in the third phase is avoided.

Thus it will be realized that when a striking pulse is applied by a hammer to a character the corresponding type-carrying shoe oscillates between its downstream and upstream shock-absorbers enabling the character to roll without friction over the assembly ink ribbon/- write medium. Consequently there is no friction pulling the paper along and a printer print is achieved.

The invention may also be applied to drum printers. A drum printer according to the invention is partially shown in FIG. 7. This illustration is a side view of the section of the type-carrier (I00), of the ink ribbon (I28), of the writing support (127) and of one hammer (I) (in a side view only a single hammer is shown). These parts all lie in a vertical plane. The carrier is a hollow cylindrical drum revolving with a uniform speed V around a horizontal axle which is perpendicular to the plane of the illustration and passing through point 0. To enhance the clarity of this illustration the typecarrying shoes (I05), (I06), (1107), the visco-elastic shock-absorbers (IM) to (II7), the metallic core (I23) of the drum (I00) are enlarged in relation to the real dimensions of the drum.

The shoes (I05) to (I07) have a form similar to that of the shoes (I) to (7) shown in FIGS. 2 and 3. Each shoe is enclosed between two visco-elastic shockabsorbers. Thus the shoe (I05) for example, is enclosed between the shock-absorbers (1M) and For the shoe (I05), the damper (I14) is the upstream shock-absorber, the damper (I15) is the downstream shock-absorber. For the shoe (106) the damper (II5) is the upstream" shock-absorber and damper (M6) is the downstream" shock-absorber. ln rest position, the sides (I511), (MEI), (I71) of the shoes (I05) to (I07) are pressed against their respective downstream shock-absorbers (IIS), (116), and (II7) while the sides (I52) to (I62), and (I72) are not in contact with the upstream dampers (I14), (115), (I I6). In the rest position, it may be seen that the shoes (I05) to (I07) are inclined at an angle a relative to respective radii of the core (I23) which pass through and are perpendicular to the core at the points 05, 06, 07. The operation of the drum printing machine according to the invention is identical with that of the linear-type carrying printer according to the invention. It is, therefore, best to refer to FIG. 6 for a better comprehension of the latter by considering the illustration as a lateral view instead of view looking down.

It must be clearly understood that the invention is in no way limited to the two printing devices described above, but that it may also be applied to any linear-type carrier such as chains with pushed blocks, typecarrying chains, type-carrying belts called time belt. It is moreover, applicable to carriers of the rotating type, such as type-carrying wheels or disks.

What is claimed is:

1. Printing device comprising a type carrier and a write medium, means supporting the type carrier for passing motion relative to the writing medium, a strike assembly for applying striking pulses to the writing medium by means of hammers, means mounting the write medium to be placed in contact with the type carrier when the striking pulses are applied thereto by said srike assembly, characterized in that the type carrier comprises a base having thereon a material coating which includes at least partially a substance with a weak energy-restoration power, said material coating holding a set of shoes of which each bears at least one type character, and each shoe being in a groove in said substance and being partially enclosed in said substance in a manner so as to be capable of tilting within the substance relative to said base when a striking pulse is applied by a hammer to the character which it carries, each groove and respective shoe having opposing contacting surfaces for limiting tilting of said shoe within its respective groove and the relationship between contacting surfaces of each groove and a respective shoe is one wherein each type face is tilted at a preselected small angle to said base.

2. The printing device according to claim I, characterized by said substance being visco-elastic.

3. The printing device according to claim 1, characterized by the base being an endless metallic belt mounted on two pulleys.

4. The printing device according to claim 1, characterized by the base being a rigid cylindrical drum.

5. The printing device according to claim I, characterized by the shoes being singularly enclosable in said substance.

6. The printing device according to claim 2., characterized by said substance being an elastomer.

7. A printer apparatus for impact printing characters onto a print medium wherein a movable carrier of type characters moves its type characters past a print medium in a predetermined direction and an impacting apparatus selectively impacts said print medium with the moving characters, said movable carrier of type characters comprising:

a base;

a layer of material disposed on said base, said layer of material containing a plurality of grooves therein, said grooves extending substantially normal to said direction of carrier movement, each groove having a throat and an open mouth and comprising a pair of rounded shoulders at the mouth of said groove, said rounded shoulders terminating at the throat of said groove which defines the narrowest width of said groove, said groove furthermore comprising a cavity upwardly of said throat, said cavity having a width substantially larger than said throat; and

a plurality of shoes, each shoe containing at least one type character thereon, each of said shoes having an end releaseably received in said cavity and which end is substantially wider than the throat of the groove,

a type face containing at least one character projecting out of said groove; and

a stem connecting said type face to said insertable end, said stem having thickness approximately equal to the width of the throat with each shoe being releaseably retained in a respective groove within said layer of material by the interlocking of the shoe end in its respective cavity for limited rocking movement transversely of said groove relative to said base in response to engagement of the type carrier with print medium during movement of said carrier, and said stem and said groove defining contactable surfaces for effecting said limiting of rocking of the respective shoe, and the bottom of each cavity comprises at least a portion of said base and said end of each shoe has a rounded bottom which contacts the portion of said base so as to define a pivotal point for said shoe.

8. The printer apparatus of claim 7 wherein each groove is spaced apart from adjacent grooves so that the rounded shoulders of adjacent grooves form a rounded surface of substantially the same curvature, said rounded shoulders acting independent of each other with respect to absorbing movement of their respective shoes.

, 9. The printer apparatus of claim 8 wherein said layer of material consists of a visco-elastic substance.

10. The printing device according to claim 7 characterized by the base being an endless metallic belt mounted on two pulleys.

11. The printing device according to claim 7 characterized by the base being a rigid cylindrical drum.

12. A printer apparatus for impact printing characters onto a print medium wherein a movable carrier of type characters moves its type characters past a print medium in a predetermined direction and an impacting apparatus selectively impacts said print medium with the moving characters, said movable carrier of type characters comprising:

a base;

a layer of material disposed on said base, said layer of material containing a plurality of grooves therein, said grooves extending substantially normal to said direction of carrier movement, each groove having a throat and an open mouth and comprising a pair of rounded shoulders at the mouth of said groove, said rounded shoulders terminating at the throat of said groove which defines the narrowest width of said groove, said groove furthermore comprising a cavity upwardly of said throat, said cavity having a width substantially larger than said throat; and

a plurality of shoes, each shoe containing at least one type character thereon, each of said shoes having an end releaseably received in said cavity and which end is substantially wider than the throat of the groove,

a type face containing at least one character projecting out of said groove; and

a stem connecting said type face to said insertable end, said stem having thickness approximately equal to the width of the throat with each shoe being releaseably retained in a respective groove within said layer of material by the interlocking of the shoe end in its respective cavity for limited rocking movement transversely of said groove relative to said base in response to engagement of the type carrier with print medium during movement of said carrier, and said stem and said groove defining contactable surfaces for effecting said limiting of rocking of the respective shoe, and the relationship between contacting surf-ces of each groove and a respective shoe is one wherein each type face is tilted at a preselected small angle to said base.

13. The printing apparatus of claim 12 wherein the tilt of each type face is towards said base in said predetermined direction.

14. The printer apparatus of claim 13 wherein each groove is spaced apart from adjacent grooves so that the rounded shoulders of adjacent grooves form a rounded surface of substantially the same curvature, said rounded shoulders acting independently of each other with respect to absorbing movement of their respective shoes.

15. The printer apparatus of claim 12 wherein the bottom of each cavity comprises at least a portion of said base and said end of each shoe has a rounded bottom which contacts the portion of said base so as to define a pivotal point for said shoe. 

1. Printing device comprising a type carrier and a write medium, means supporting the type carrier for passing motion relative to the writing medium, a strike assembly for applying striking pulses to the writing medium by means of hammers, means mounting the write medium to be placed in contact with the type carrier when the striking pulses are applied thereto by said srike assembly, characterized in that the type carrier comprises a base having thereon a material coating which includes at least partially a substance with a weak energy-restoration power, said material coating holding a set of shoes of which each bears at least one type character, and each shoe being in a groove in said substance and being partially enclosed in said substance in a manner so as to be capable of tilting within the substance relative to said base when a striking pulse is applied by a hammer to the character which it carries, each groove and respective shoe having opposing contacting surfaces for limiting tilting of said shoe within its respective groove and the relationship between contacting surfaces of each groove and a respective shoe is one wherein each type face is tilted at a preselected small angle to said base.
 2. The printing device according to claim 1, characterized by said substance being visco-elastic.
 3. The printing device according to claim 1, characterized by the base being an endless metallic belt mounted on two pulleys.
 4. The printing device according to claim 1, characterized by the base being a rigid cylindrical drum.
 5. The printing device according to claim 1, characterized by the shoes being singularly enclosable in said substance.
 6. The printing device according to claim 2, characterized by said substance being an elastomer.
 7. A printer apparatus for impact printing characters onto a print medium wherein a movable carrier of type characters moves its type characters past a print medium in a predetermined direction and an impacting apparatus selectively impacts said print medium with the moving characters, said movable carrier of type characters comprising: a base; a layer of material disposed on said base, said layer of material containing a plurality of grooves therein, said grooves extending substantially normal to said direction of carrier movement, each groove having a throat and an open mouth and comprising a pair of rounded shoulders at the mouth of said groove, said rounded shoulders terminating at the throat of said groove which defines the narrowest width of said groove, said groove furthermore comprising a cavity upwardly of said throat, said cavity having a width substantially larger than said throat; and a plurality of shoes, each shoe containing at least one type character thereon, each of said shoes having an end releaseably received in said cavity and which end is substantially wider than the throat of the groove, a type face containing at least one character projecting out of said groove; and a stem connecting said type face to said insertable end, said stem having thickness approximately equal to the width of the throat with each shoe being releaseably retained in a respective groove within said layer of matErial by the interlocking of the shoe end in its respective cavity for limited rocking movement transversely of said groove relative to said base in response to engagement of the type carrier with print medium during movement of said carrier, and said stem and said groove defining contactable surfaces for effecting said limiting of rocking of the respective shoe, and the bottom of each cavity comprises at least a portion of said base and said end of each shoe has a rounded bottom which contacts the portion of said base so as to define a pivotal point for said shoe.
 8. The printer apparatus of claim 7 wherein each groove is spaced apart from adjacent grooves so that the rounded shoulders of adjacent grooves form a rounded surface of substantially the same curvature, said rounded shoulders acting independent of each other with respect to absorbing movement of their respective shoes.
 9. The printer apparatus of claim 8 wherein said layer of material consists of a visco-elastic substance.
 10. The printing device according to claim 7 characterized by the base being an endless metallic belt mounted on two pulleys.
 11. The printing device according to claim 7 characterized by the base being a rigid cylindrical drum.
 12. A printer apparatus for impact printing characters onto a print medium wherein a movable carrier of type characters moves its type characters past a print medium in a predetermined direction and an impacting apparatus selectively impacts said print medium with the moving characters, said movable carrier of type characters comprising: a base; a layer of material disposed on said base, said layer of material containing a plurality of grooves therein, said grooves extending substantially normal to said direction of carrier movement, each groove having a throat and an open mouth and comprising a pair of rounded shoulders at the mouth of said groove, said rounded shoulders terminating at the throat of said groove which defines the narrowest width of said groove, said groove furthermore comprising a cavity upwardly of said throat, said cavity having a width substantially larger than said throat; and a plurality of shoes, each shoe containing at least one type character thereon, each of said shoes having an end releaseably received in said cavity and which end is substantially wider than the throat of the groove, a type face containing at least one character projecting out of said groove; and a stem connecting said type face to said insertable end, said stem having thickness approximately equal to the width of the throat with each shoe being releaseably retained in a respective groove within said layer of material by the interlocking of the shoe end in its respective cavity for limited rocking movement transversely of said groove relative to said base in response to engagement of the type carrier with print medium during movement of said carrier, and said stem and said groove defining contactable surfaces for effecting said limiting of rocking of the respective shoe, and the relationship between contacting surf-ces of each groove and a respective shoe is one wherein each type face is tilted at a preselected small angle to said base.
 13. The printing apparatus of claim 12 wherein the tilt of each type face is towards said base in said predetermined direction.
 14. The printer apparatus of claim 13 wherein each groove is spaced apart from adjacent grooves so that the rounded shoulders of adjacent grooves form a rounded surface of substantially the same curvature, said rounded shoulders acting independently of each other with respect to absorbing movement of their respective shoes.
 15. The printer apparatus of claim 12 wherein the bottom of each cavity comprises at least a portion of said base and said end of each shoe has a rounded bottom which contacts the portion of said base so as to define a pivotal point for said shoe. 